Project Summary Renal cell carcinoma (RCC) is an aggressive and highly metastatic cancer with rising incidence worldwide. Forty percent of patients with localized RCC show tumor recurrence and progression. Patients with advanced RCC respond poorly to therapeutic intervention and only 10% survive five years past diagnosis. In more than half of all renal cancers, the von-Hippel Lindau tumor suppressor is defective leading to the upregulation of septin 2 (SEPT2), a member of the septin family of GTPases. Septins are evolutionarily related to the Ras oncogenes and are being used as biomarkers for colorectal and urological cancers. To date, it is completely unknown how septins function in RCC progression and metastasis. Our preliminary data show that SEPT2 is required for RCC migration and the assembly of focal adhesions to the extracellular matrix (ECM), which is essential for directionally persistent migration. We hypothesize that SEPT2 promotes RCC migration by regulating the assembly and organization of actin stress fibers at sites of RCC-matrix adhesion. Here, we will explore mechanistic tenets of this hypothesis and test septin GTPases as therapeutic targets for RCC metastasis. Specifically, this project aims to: i) determine the role of SEPT2 in the assembly of focal adhesions with the ECM, ii) identify the mechanism by which SEPT2 regulates the organization of the actin stress fiber network of RCCs, and iii) examine how alterations and pharmacological targeting of SEPT2 expression affect RCC motility in three-dimensional (3D) matrices that mimic in vivo tumor microenvironments. These aims will be achieved through a collaborative mentoring program by leading investigators in the areas of septin biology, actin cytoskeleton and cancer cell migration. The proposed research plan involves training in cutting edge methodologies of light and electron microscopy, and 3D models of tissue culture. Courses, conferences, speaking and writing engagements will ensure training in the fundamentals of cell migration and translational cancer research. In summary, this project will provide a novel insight into the role of SEPT2 in RCC migration and the efficacy of SEPT2-targeted approaches for the treatment of RCC metastasis, leading the way to an independent career in cancer cell biology.